Question: What W3C is recommended for the Hypertext Transfer Protocol?
Paraphrase: What W3C is prescribed for the Hypertext Exchange Convention?
SPARQL (Wikidata):  select distinct ?sbj where { ?sbj wdt:P1547 wd:Q8777 . ?sbj wdt:P31 wd:Q2661442 } 
Answer: SPARQL 1.1 Protocol, SPARQL Protocol for RDF